1. Field of the Invention
The invention relates to brine-feeding means for, inter alia, diaphragm-type electrolytic cell apparatus. Though the invention may be practiced with respect to a single cell, it is likely to be used with a plurality of cells, such as all the cells in a chlor-alkali cell room.
2. Description of the Prior Art
Although there have been suggestions in the prior art of brine-cell feeding structures that are more complicated or introduce the brine vertically or below the liquid level in the cell (see, for example, U.S. Pat. Nos. 1,924,822; 2,669,122; and 2,673,232), the usual practice has been to introduce the brine through a brine introduction tube which is about 16 millimeters (5/8 inch) in outside diameter and has a resilient brine-supply line connected to its outside end, covering where the orifice member is located.
The structure described above has a few drawbacks. It is not possible to tell, without disengaging the brine supply line, whether an orifice is clogged or the difficulty is upstream of the orifice. Even more troublesome is the variation in brine flow rate which occurs, because with such apparatus, either of two modes of flow may occur. In one mode, which can be called "normal flow", the brine enters the cell in the form of a jet, as is desirable. In another mode, which can be called "siphon flow", the brine-introduction tube inboard of the orifice becomes filled with liquid, and when this happens, there are two main effects: (1) even with the same hydrostatic head from the brine-supply line, the rate of introduction of brine to the cell increases by about 15 percent, and (2) the leakage current through the brine-supply line increases from about 0.1 milliampere to a high value, possibly as much as 1 ampere. With the apparatus used prior to the present invention, such changes in mode of flow have occurred sporadically and unpredictably, making it relatively more difficult to keep a roomful of cells operating upon a smooth basis. The strength of the caustic produced by an individual cell is importantly influenced by the brine flow-rate, and it is also important to maintain liquid levels in the cells within design limits to avoid safety hazards.